Vapor deposition systems and methods

ABSTRACT

Vapor deposition systems and methods associated with the same are provided. The systems may be designed to include features that can promote high quality deposition; simplify manufacture, modification and use; as well as, reduce the footprint of the system, amongst other advantages.

RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.13/304,676, filed Nov. 27, 2011, which is a continuation of U.S.application Ser. No. 11/167,570, filed Jun. 27, 2005, now U.S. Pat. No.8,202,575, which claims priority to U.S. Provisional Application No.60/583,854, filed Jun. 28, 2004, and U.S. Provisional Application No.60/652,541, filed Feb. 14, 2005, each of which are incorporated hereinby reference in their entirety.

FIELD OF INVENTION

The invention relates generally to vapor deposition systems and methods,and more particularly, to atomic layer deposition systems and methods.

BACKGROUND OF INVENTION

Atomic layer deposition (ALD) is a technique that allows growth of thinfilms, atomic layer by layer. The technique can be illustrated with, butis not limited to, the deposition of Al₂O₃ from water and trimethylaluminum (TMA) precursors. Recipes for many other materials producinginsulators, metals and semiconductors, can be found in literature. FIG.1 schematically shows the growth of Al₂O₃ from water and (TMA). Thegeneral steps include: (a) insert an air hydroxilated substrate into thevacuum chamber, (b,c) The TMA precursor is pulsed and the TMA will reactwith the OH on the surface. TMA does not react with itself and theformed monolayer, thus passivating. (d) The unreacted TMA molecules areremoved by evacuation and/or purging with an inert gas such as nitrogenor argon (e,f) Water is pulsed into the reactor. This will remove theCH₃ groups, create Al—O—Al bridges and passivates the surface withAl—OH. CH₄ (methane) is formed as a gaseous by-product (g) Unreacted H₂Oand CH₄ molecules are removed by evacuation and/or purging withnitrogen, (a-g) is called a cycle and each cycle produces about 1.1Angstrom of Al₂O₃. Thus, 100 cycles produces 110 Angstrom of Al₂O₃.

Design of ALD systems has followed different approaches, some of whichare based on deposition systems used for other deposition techniques(e.g., chemical vapor deposition).

One approach is the laminar flow tube furnace, as shown in FIG. 3. Inthis case, a substrate 28 is inserted into a tube 24 through an accessport 36. The substrate is heated using a tube furnace heater 26 and thereaction chamber inside the tube 24 is evacuated using a pump 34. Thepressure is measured with a vacuum gauge 30. A continuous inert gas flow(carrier gas) is supplied from a cylinder 10 and injected into theprecursor lines using inert gas lines 12. The precursors are heatedusing an oven 14. Precursor vapor is pulsed from precursor containers 16and 20, using electronically controlled valves 18 and 22. These types ofreactors are often found in research environments and are generally moresuitable for small substrates, since large substrates increase the tubefurnace size dramatically, both in diameter and length, in order tomaintain sufficient temperature uniformity. The design is based on CVDsystems, where very high temperatures are typically used and lowtemperature O-ring access is displaced from the tube furnace heater.

A second ALD system design also derived from the CVD technology is shownin FIG. 4. In this case, a shower head 42 is used to supply theprecursors in an effort to uniformly disperse, the chemicals over thesurface. In such designs, the substrate heater is generally found insidethe vacuum space. Although the showerhead vapor injection design may beeffective in CVD systems, where gas or vapor is injected that onlyreacts at the high substrate temperature site, and where uniform gasdistribution is essential for uniform film thickness, such a design canlead to clogging in ALD systems where precursor residues can react witheach other at showerhead temperature. Moreover, in contrast to certainCVD processes, ALD does not typically require very uniform dispersion ofthe precursor do to the self-limiting nature of the process. Inaddition, in order to prevent condensation of precursors, the showerheadand other parts of the system are generally heated to a temperaturerange of 1.00-200° C., which can be complicated for complex geometriessuch as showerheads. Lastly, because of the large surface area and smallcavities, the evacuation and purging of precursor in the depositioncycles can be difficult.

For production ALD systems, usually deposition stations are combined ina cluster tool arrangement. Wafers racks are inserted into a load lock,transferred in a transfer chamber through a slit valve arrangement. Arobotic arm moves the substrates to the deposition station, where it isstacked vertically with other substrates using a vertical translationrobot. After deposition the substrates are removed through, unload-lock.

A single unit system is generally characterized by a horizontalprecursor gas flow, and horizontal access port (slit valve) in thefront. The height of the single unit defines the internal reactor volumeand precursor flow speed, and is optimized for fast flow and gasutilization, and for one specific substrate type, thickness and diameter(usually silicon wafers).

Because of the complex nature of the design to achieve large throughputfor one particular type of substrate, modification, upgrading, cleaningand repair can be very time consuming, and the systems do not lendthemselves for research and development purposes.

Most ALD systems thus far have focused deposition on planar substratessuch as silicon wafers, or, in the case of tube furnaces, wafer pieces,even though the ALD technique can be used to coat complex 3D structures,such as capacitor trenches, nanotubes, plastics, inverse opals,catalytic beds, photonic crystals, engine components, tools, opticalparts etc. Since the ALD technology is highly scalable to largedimension samples, research of this technique in fields other than thesemiconductor industry is desired and a tool that is easily adapted to avariety of samples geometries can be advantageous.

SUMMARY OF INVENTION

Vapor deposition systems and methods are provided, as well as componentsused in such systems and methods.

In one aspect, the invention provides an atomic layer deposition system.The system includes a reaction chamber designed to enclose a substrate.The reaction chamber has a top surface, a bottom surface and a sidewallbetween the top and bottom surfaces. A first precursor supply isconnected to a precursor port formed in the bottom surface. A secondprecursor supply is connected to a precursor port formed in the bottomsurface. An outlet port is formed in the bottom surface.

In another aspect, the Invention provides an atomic layer depositionsystem. The system includes a reaction chamber designed to enclose asubstrate. The reaction chamber has a top surface, a bottom surface anda sidewall between the top and bottom surfaces. A first precursor supplyand a second precursor supply are connected to a precursor port formedin the bottom surface.

In another aspect, the invention provides an atomic layer depositionprocess. The process includes positioning a substrate in a reactionchamber having a top surface, a bottom surface and a sidewall betweenthe top and bottom surfaces. The process further includes introducing afirst precursor into the reaction chamber through a precursor portformed in the bottom surface and removing gaseous species through anoutlet port formed in the bottom surface. The process further includesintroducing a second-precursor in to the reaction chamber through aprecursor port formed in the bottom surface and removing gaseous speciesthrough the outlet port formed in the bottom surface.

In another aspect, the invention provides a trap designed for use in avapor deposition system to trap gaseous species. A majority of thesurface area of the trap is substantially parallel to flow of gaseousspecies through the trap.

Other aspects, embodiments and features of the invention will becomeapparent from the following detailed description of the invention whenconsidered in conjunction with the accompanying drawings. Theaccompanying figures are schematic and are not intended to be drawn toscale. In the figures, each identical, or substantially similarcomponent that is illustrated in various figures may be represented by asingle numeral or notation (though not always). For purposes of clarity,not every component is labeled in every figure. Nor is every componentof each embodiment of the invention shown where illustration is notnecessary to allow those of ordinary skill in the art to understand theinvention. All patent applications and patents incorporated herein byreference are incorporated by reference in their entirety. In case ofconflict, the present specification, including definitions, willcontrol.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an atomic layer deposition process.

FIG. 2A is a typical timing diagram for an ALD valve pulsing process.

FIG. 2B is a typical timing diagram for an ALD gas pulsing-pumpingprocess.

FIG. 2C is a typical timing diagram for an ALD gas pulsing-purgingprocess.

FIG. 2D is a typical timing diagram for a stop valve assisted ALD gaspulsing-pumping process.

FIG. 3 is an example of an ALD tube furnace reactor system withhorizontal laminar gas flow.

FIG. 4 is an example of an ALD deposition system with shower head gasinjection.

FIG. 5 is an isometric view of an ALD cabinet and reactor assemblycombination according to an embodiment of the present invention.

FIG. 6 is an isometric view of a reactor assembly according to anembodiment of the present invention.

FIG. 7A is an exploded isometric view of a reactor assembly according toan embodiment of the present invention.

FIG. 7B is an isometric view of a reactor assembly showing gas inlinetees according to an embodiment of the present invention.

FIG. 8 is an isometric bottom view of a reactor according to anembodiment of the present invention.

FIG. 9 is an isometric view of the a cabinet with precursor lineassembly, pumping line assembly, pump (partial view), RTD (resistortemperature detector) temperature sensors and reactor feed through andfixing holes according to an embodiment of the present invention.

FIG. 10 is an isometric top view of an ALD reactor according to anembodiment of the present invention.

FIG. 11A is a top view of a reactor according to an embodiment of thepresent invention, with cross section line indication (“C”).

FIG. 11B is a cross section of the reactor at section line “C” of FIG.11A. according to an embodiment of the present invention.

FIG. 12A is a top lid with expanded cavity for thicker substratesaccording to an embodiment of the present invention.

FIG. 12B is a top lid with protruding lid for thinner substrates orreduced precursor consumption or more uniform vapor flow according to anembodiment of the present invention.

FIG. 13 is a screenshot of the control software programmed in “Labview”,used in an embodiment of the invention to control an ALD system.

FIG. 14 shows the results of the thickness distribution in Angstroms, ofan exemplary Al₂O₃ atomic layer deposition run on a 4-inch silicon waferaccording to a method of the invention, as measured with anellipsometer.

FIG. 15 shows the attachment of an NW tee to reactor, gauge and stopvalve according to an embodiment of the invention.

FIG. 16 shows the attachment of a heater block to a tee according to anembodiment of the invention.

FIG. 17 shows the attachment of two reflector plates in a pumping linesection according to an embodiment of the invention.

FIG. 18 shows a precursor line and pulse valve heating assemblyaccording to an embodiment of the invention.

FIG. 19 shows a pumping line .heating jacket according to an embodimentof the invention.

FIG. 20 shows a manifold for expanding the number of precursor linesaccording to an embodiment of the invention.

FIG. 21 shows one half of a manifold heater block according to anembodiment of the invention.

FIG. 22 shows a manifold heater block assembly according to anembodiment of the invention.

FIG. 23 shows an O-ring groove design according to an embodiment of theinvention.

FIG. 24 is an isometric view of a reactor assembly that includes asingle precursor port according to an embodiment of the presentinvention.

FIG. 25 is a top view of a reactor that includes a single precursor portaccording to an embodiment of the present invention.

FIG. 26 is a section view of a reactor assembly that includes a trapmaterial positioned in an outlet port according to an embodiment of theinvention.

FIG. 27 shows a trap material according to an embodiment of theinvention.

ENUMERATION OF FEATURES IN THE FIGURES

10 50, 52 Precursor valve pulse widths

54, 56, 58 Pumping down

55 Pressure after first precursor pulse

57 Pressure after second precursor pulse

60, 62, 64 Inert gas flow (purge)

61 Inert gas flow+first precursor pulse

63 Inert gas flow+second precursor pulse

66, 68, 70 Stop valve open (pumping)

70 After first precursor valve pulse

69 After second precursor valve pulse

10 Inert gas supply

12 Inert gas supply lines

14 Precursor heating oven

16 First precursor

18 First precursor pulse valve

20 Second precursor

22 Second precursor pulse valve

24 Reactor tube

26 Tube furnace heaters

28 Substrate

30 Vacuum, gauge

32 Pumping line

34 Vacuum pump

36 Substrate access

38 Substrate heater

40 Vacuum chamber

42 Shower head precursor vapor supply

100 Reactor assembly

102 Stainless steel reactor base body

105 Aluminum, reactor lid

106 Handle

108 Handle rubber

110 Hinges

112 Wafer space

114 O-ring groove

116 O-ring

118 First precursor port

120 Second precursor port

122 Output (pumping line) port

124 Substrate heater

125 Nut holding substrate heater

126 Outer tubular heater

128 Dual function threaded bolts; fixing tubular heater and reactor tocabinet

130 RTD center temperature hole

132 RTD center

134 RTD wall temperature hole

136 RTD wall

138 Thin reactor body profile

140 Reactor space

142 Expanded reactor lid

144 Expansion area

146 Reaction chamber protruding lid

148 Protrusion

202 First precursor cylinder

204 Manual valve

206 Pulse valve for first precursor

208 VCR union for first precursor line

210 Second precursor cylinder

212 Pulse valve for second precursor

214 VCR union tor second precursor line

302 Vacuum pump

304 Bellows

306 Solenoid stop valve

308 KF cross

310 Solenoid vent valve

312 Vacuum gauge

402 Cabinet access door

404 Cabinet top

406 Left side panel

408 Right side panel

412 Bottom

414 Frame

416 Hole for first precursor ports

417 Hole for second precursor port

418 Hole for pumping port

420 Four holes for fixing bolts

422 Outer RTD mounted to cabinet top

423 Inner RTD mounted to cabinet top

424 Holes for outer (tubular) heater

426 Electrical wire feed through hole for substrate heater

502 Three port pulse valve for first precursor

504 Precursor input port

506 Precursor+inert gas output port

508 Inert gas input port

512 Three port pulse valve for second precursor

514 Precursor input port

516 Precursor+inert gas output port

518 Inert gas input port

520 NW tee

522 Aluminum heater half block left, pumping line assembly

524 Aluminum heater half block right, pumping line assembly

526 Heater cartridge hole

528 Screw holes in heater halves for mounting the halves together,forming the tee or cross heater block

530 Pumping line assembly heat reflection plate, right side

532 Pumping line assembly heat reflection plate, left side

540 Precursor valves heater half block left.

542 Precursor valves heater half block right.

544. Precursor valves heater reflection plate left.

546. Precursor valves heater reflection plate right.

550. Pumping line heating jacket.

600. Precursor line welded manifold.

602. Precursor line manifold heating block, right half.

604. Precursor line manifold heating block, left half.

606. Precursor line manifold heating block reflector plate, right.

608. Precursor line manifold heating block reflector plate, left.

620. Single precursor port

622. Bottom surface of the reactor chamber according to an embodiment ofthe present

624. Outlet port of reactor chamber

625 a, 625 b, Manifold inlets

626, Manifold

628. Manifold outlet

630. Trap

DETAILED DESCRIPTION OF INVENTION

The invention provides atomic layer vapor deposition systems and methodsassociated with the same. The systems include a reaction chamber thatenclose a substrate (or more than one substrate). Precursor (e.g.,reactive species) supplies are connected to the reaction chamber througha port (or ports) to introduce suitable precursors into the chamber. Insome cases, multiple precursor supplies are connected to a singleprecursor port; while, in other cases, each precursor supply may beconnected to separate, respective ports. An outlet port may also beprovided in the reaction chamber, for example, to remove gaseous species(e.g., unreacted precursor, reaction products, inert gas) at certainpoints during the process. The system includes an arrangement of heaterswhich provide suitable temperature conditions to promote a reactionbetween the precursors to deposit a material layer on the substrate. Asdescribed further below, the systems of the invention may be designed toinclude features that can promote high quality deposition; simplifymanufacture, modification and use; as well as, reduce the footprint ofthe system, amongst other advantages.

In certain embodiments, it is preferable for the precursor port (orports) to be formed in a bottom surface of the reaction chamber (e.g.,between an outer tubular heater and substrate sections). In some cases,it is preferable for all of the precursor ports (whether there is asingle post or multiple ports) to be formed in the bottom surface. Inthese cases, the top surface (e.g., lid) and sidewall of the reactionchamber may be free of precursor ports. When the precursor port(s) areformed in the bottom surface, it may be preferable for the port(s) tolead directly into the reaction chamber as shown in the illustrativeembodiments.

As described further below and illustrated in certain figures,positioning the precursor port(s) in the bottom surface of the reactionchamber can reduce the footprint of the system which can save valuableclean room space. The footprint can be reduced, in part, by facilitatingthe attachment of the ports to the precursor supplies. For example, theprecursor supplies may be positioned, in a cabinet below the reactionchamber (e.g., See FIG. 5) and connected to ports using supply linesthat can having simple designs. In some cases, the supply lines mayextend vertically in a substantially straight line from the precursorsupplies directly to the respective precursor ports (e.g., inembodiments including multiple ports); while, in other cases, the supplylines may extend vertically in a substantially straight line to amanifold (e.g., in embodiments including a single port) which may befurther connected to a precursor port using another straight line supplyline. The straight vertical geometry of the precursor lines allow themto simply dangle from the reaction chamber where no additional supportis required, and in direct proximity to the precursor supplies.Moreover, the vertical attachment and/or orientation of the precursorlines has manufacturing and assembly advantages. For example, this canfacilitate connecting precursor line(s) to the port(s), as well asattachment of heater jackets to precursor lines to keep the lines at adesired elevated temperature (e.g., 135° C.) to prevent condensation ofprecursor.

In certain embodiments, the outlet port of the system is formed in thebottom surface of the reaction chamber. It may he preferred in certainembodiments for both the precursor port(s) and the outlet port to beformed in the bottom surface. In these embodiments, the top surface(e.g., lid) and sidewall of the reaction chamber may be tree of alltypes of ports. In some cases, the outlet port may be positionedrelative to the precursor port(s) such that the substrate Is between theprecursor port(s) and the outlet port. For example, the outlet port maybe on a substantially opposite side of the substrate as the precursorport(s) (e.g., See FIGS. 11A and 25).

Positioning the outlet port in the bottom surface of the reactionchamber can reduce the footprint of the system for similar reasons asdescribed above in connection with the precursor port(s). For example,the footprint can be reduced by facilitating attachment of the port to avacuum pump. For example, the vacuum pump may be positioned in a cabinetbelow the reaction chamber (e.g., See FIG. 5) and connected to the portusing a pumping line that has a simple design. In some cases, thepumping line may extend vertically in a substantially straight line atleast part of the distance between the vacuum and the port The straightvertical geometry of the line can allow it to simply dangle from thereaction chamber where no additional support is required, and in directproximity to the vacuum. Also, the vertical attachment and orientationof the pumping lines can facilitate manufacturing, assembly andcleaning.

Positioning the precursor and outlet ports at the bottom, surface of thereaction chamber can allow the height of the reactor base to he small,while providing a relatively large outlet port opening. This combinationof low reactor height and large outlet port decreases heat-up and pumpdown time and improves throughput.

The vapor deposition systems of the invention may be designed to promotebeneficial heating conditions. For example, as described further below,the system may include separate heaters which heat the substrate areaand other areas of the chamber (e.g., o-ring, lid, sidewalls)separately. Such a design enables the temperature of the substrate to bemaintained relatively high (e.g., about 600° C.), while maintaining theother areas relatively low (e.g., about 150° C.). The substrate area maybe heated, for example, by an external heater (e.g., a disc heater) thatis positioned outside of the reaction chamber (e.g., beneath thereaction chamber) and heats the substrate area by thermal conductance.The other areas of the chamber may also be heated by a tubular heaterexternal to the reaction chamber. Thus, in some embodiments, no healersmay be enclosed by the reaction chamber. Differential temperaturebetween the substrate area and other areas of the reaction chamber mayfurther he enhanced by spacing the reactor base above a supportingsurface (e.g., die top surface of a cabinet), using the air spacein-between as an insulating medium that prevents thermal conductancefrom the substrate heater to the outside O-ring area.

In some embodiments, the lid can be made of a high thermal conductancematerial such as aluminum or copper, or when transparency is desired,sapphire. The outer tabular heater attached to the reactor base can heatthe lid to a sufficient temperature by thermal conductance once thevacuum pulls the lid in mechanical contact with the reactor base. Thehigh thermal conductance of the lid promotes temperature uniformitythroughout the lid and may eliminate the need for a separate ltd heater.Thus, in certain embodiments, the lid is free of a heater which cansimplify design and maintenance, as well as allowing the lid to bereplaced, easily (e.g., in different processes which to allow fordifferent substrate geometries or to induce certain flow patterns).

FIG. 5 illustrates a vapor deposition system according to one embodimentof the invention. In the illustrative embodiment, the vapor depositionsystem is an atomic layer deposition (ALD) system. However, it should beunderstood that certain embodiments of the invention are not limited toALD and are applicable to others types of vapor deposition systemsincluding chemical vapor deposition (CVD) systems.

In this illustrative embodiment, a cabinet includes a door 402, sidepanels 406 and 408, and a top 404. The cabinet provides space forvarious components of the system including: precursor line and pumpingline components (described further below), control electronics, vacuumpump 302, precursor cylinders 202 and 210, and their heater jackets. Abottom 412 of the cabinet may be open to allow the pump to be positionedon the floor. This advantageously limits transfer of vibration from pump302 to cabinet and reactor. In this embodiment, temperature sensors(e.g., resistor temperature devices (RTDs)) 422 and 423 are mounted onthe top 404 of the cabinet. As shown, the pumping and precursor line arevertically suspended from the reactor assembly 100. The controlelectronics may be located as an enclosure, inside the cabinet and areconnected to a personal computer using a universal serial bus (USB)interface. Heater jackets may surround different components of thesystem that are described further below including precursor cylinders202, 204, precursor solenoid valves, output line cross and bellows.Temperature sensors may be provided on these components (e.g., valvesand vacuum gauge) to ensure that the components stay sufficiently warmenough to prevent condensation of vapors, but still within the specifiedtemperature range.

FIGS. 6 and 7 illustrate different views of components of a depositionsystem (without the cabinet and pump) according to one embodiment of theinvention. FIG. 6 shows a view in which the precursor lines and pumpingline are connected, and FIG. 7A shows an exploded view. A reactor base102 of the system has a substrate area 112, an O-ring groove 114, anO-ring 116, hinges 110, a lid 105 and handle 106. In certainembodiments, it is preferred that the reactor base is formed of a lowthermal conductivity material, such as stainless steel. It may also hepreferred that the handle be formed of a thin walled low thermalconductivity material (e.g., stainless steel) to allow opening of thereactor, even while the reactor top is at an elevated temperature (e.g.,100-200° C.). In some cases, the handle is surrounded, in part, by aninsulating portion (e.g., formed of cold touch rubber) 108 to providethermal insulation from the elevated temperatures.

O-ring groove 114 is shown in more detail in FIG. 23. In certainconventional deposition systems, half-dovetail groove designs can beused to lock an O-ring in place and provide sufficient space forexpansion. A half-dovetail creates a cavity in the corner below theO-ring groove, which acts as a virtual leak. Especially in atomic layerdeposition, where it is preferable to remove one precursor completely,before letting in the second precursor, it may be important to limit thepresence of such cavities. In certain embodiments, the system includes amodified half-dovetail groove design. One modification used in certainembodiments of the invention is that the vacuum side of the groovebottom is rounded, with a radius comparable or slightly less than thatof the O-ring. A radius of 0.070 inch in shown in FIG. 23, which can besuitable, for example, with an ⅛ inch cross sectional diameter O-ring.In this design, the only cavity is on the atmospheric (right) side ofthe bottom, of the O-ring, in the dovetail, but since this is on theatmospheric side, it does not create a virtual leak. A secondmodification of a standard half-dovetail groove, used in certainembodiments of the invention, is that the vacuum side (left side in thedrawing) has an O-ring supporting edge that is slightly lower (e.g.,0.010 inch) than the top of the reactor body. This facilitates quickevacuation of gas.

All dimensions in FIG. 23 are in inches, and suitable for a ⅛″ diameterO-ring, However, it should be understood that other dimensions are alsopossible in different systems. Moreover, other groove designs may alsobe suitable in certain embodiments of the invention.

The illustrative embodiment of FIGS. 6 and 7 includes a first precursorport 118 and a second precursor port 120. In this embodiment, the firstprecursor supply (e.g., a precursor cylinder) 202 is connected to thefirst precursor port and the second precursor supply 210 (e.g., aprecursor cylinder) is connected to the second precursor port. However,it should be understood that other systems of the invention may includea single precursor port to which both the first precursor supply and thesecond precursor supply are connected (e.g., using a manifold having twoinlets and a single outlet; See FIGS. 24 and 25). Also, it should beunderstood that any number of precursor supplies may be used (e.g., 3,4, 5, etc.) with each precursor supply being connectable to 50respective ports in the reaction chamber, or all precursor suppliesconnected to a single port (e.g., using a manifold having multipleinlets and a single outlet).

As shown in FIGS. 6 and 7, precursor supply 202 is filled with a firstprecursor, Manual valve 204 is provided, in certain cases, to allowshipping from the chemical manufacturer of the precursor. Cylinder 202can be removed after closing manual valve 204 and replaced with anotherprecursor cylinder if desired (e.g., when the precursor has beenexhausted). Connections at the precursor side are VCR in thisembodiment, attached to the manual valve 204 is a high speed solenoidpulse valve 206, that allows injection of precursor down to themillisecond range.

The second precursor supply is configured similarly to the firstprecursor supply, except that non-aggressive precursors such as watercan be filled by the user and may not include a manual valve 204. Forexample, cylinder 210 could be filled with de-ionized water on site, andattached to solenoid valve 202 without a manual valve. A chemical, suchas trimethyl aluminum (TMA), generally needs to be filled in a glove boxand needs to be closed with a manual valve, to avoid exposure to air.Subsequently it can be connected to solenoid valve 206 and manual valve204 can be opened when the system is evacuated or filled with an inertgas such as nitrogen.

Typical ALD processes use an inert carrier gas (e.g., nitrogen, argon,xenon, amongst others). The carrier gas may be introduced through one(or more, if present) of the precursor ports. In certain embodiments, aninert carrier gas supply is connected to a precursor supply line. Atcertain points during processing, the inert gas may be mixed with theprecursor so that an inert gas-precursor mix is introduced into thechamber; while, at other points during processing, the inert gas may beintroduced into the chamber alone (e.g., without the precursor). Asshown in FIG. 7B, the inert gas supply may be connected to the precursorsupply line(s) using a suitable valve assembly. As shown, a line fromthe inert carrier gas supply can be hooked up to an inlet of three-portpulse valves 502 and 512 which are also connected to the precursorsupplies. This configuration enables the system to be operated in ALDmode 2 which is discussed further below. Operation of the valves can becontrolled, as described further below, to control introduction of theinert gas and/or precursor into the chamber.

These inert carrier gas supply lines may include other valves and/ormass flow controllers. For example, a mass flow controller may be usedfor the inert gas supply. The output of the mass flow controller splitsup into however many pulse valves are mounted, so that each valvereceives the same amount of flow. Three-port pulse valve 502 has abottom input port 504 connected to the precursor supply so that thevalve can pulse the precursor. Internally, the flow path from the inertgas input line 508 of pulse, valve output 506 may always remain open incertain ALD processes. In such processes, the valve is normally closed,meaning that inlet 504 is closed when the valve is not actuated, whileat the same time, path 508 to 506 is always open. When pulsing thevalve, line 504 is opened to both line 508 and 506, but because theinert gas is coming into 508 from the mass flow controller, the inertgas-precursor mix is introduced into the reaction chamber. This “inertgas assist” process prevents one precursor from one pulse valve fromentering a second pulse valve, preventing or minimizing deposition inall valves. As shown in FIG. 7B, with two input ports on the reactor,two precursor pulse valves can be directly mounted to the VCR connectionwhich are welded to the reactor. The vent valve 310 in FIG. 7A can beremoved and cross 308 replaced by a tee, because the system can bevented after deposition using the nitrogen supply gas.

As shown in FIG. 8, a KF fitting 122 is welded to the reactor base 102to define, in past, the pumping port that is formed in the bottomsurface of the reactor. A cross 308, a vent valve 310, vacuum gauge 312and stop valve 306 can be connected to the fitting. Access to the pumplocated vertically below the reactor is a pumping line bellows 304. Whenusing the inert gas assist operation, and three-port valves 504 and 502,venting of the system can be done using the inert gas, and no separatevent valve is necessary. This configuration is shown in FIG. 15. In thisembodiment, three-port valve 502 is connected to the outlet port, the312 vacuum gauge and the stop valve 306.

Valve 502 may be heated using a heater. As shown in FIG. 16, the heatermay comprise a heater block (which may be made of a conductive materialsuch as aluminum) including two halves 522 and 524. One side has a hole526 to fit a heater cartridge. The halves are held together using boltsin holes 528. The heater is machined such that it fits both around astandard NW cross and around a standard NW tee. The two halves are inintimate contact, so that the heat from the single cartridge spreadsover both halves. A screw to mount a temperature sensor is also providedon the heater block.

FIG. 17 shows reflector halves 530 and 532 which fit around the heater524, a non-electronic part of gauge 312, and a non-electronic part ofvalve 206. The two halves may be held together by magnets, glued to theedges of each half. This allows easy mounting of these reflector plates.The reflector plates serve the purpose of both reflecting heat back intothe to be heated parts, and keeping heat out from the electronic partsand further components in the cabinet.

FIG. 18 shows the heater block for the two precursor input portconfiguration. Here two aluminum halves 540 and 542 clamp around the VCRfittings. A hole in one half of the aluminum block is provided to fit aheater cartridge. Metal reflector plates 544 and 546 are spaced (e.g.,about ¼ inch) from the aluminum heater blocks, and keep the heat in thealuminum heater blocks. The temperature sensor for the pulse valves maybe screwed onto the valves themselves. Threads in the side of the pulsevalves can be provided for this purpose.

FIG. 19 shows a standard flexible heater jacket 550 that may be used toheat the pumping line bellows 304. It should be understood that similarheater jackets may also be used to heat the precursor supply lines andvalve assemblies.

In FIG. 20, a multi-precursor manifold 600 is depicted. As shown, themanifold includes a number of inlets from respective precursor supplies.It should be understood that any suitable number of precursor supplies(e.g., 2, 3, 4, 5, etc.) may be used in connection with the manifold.Welded VCR pieces may be used to allow expansion of the number ofprecursors from two to the desired number (e.g., 3, 4, 5). In thisembodiment, the manifold includes two outlets which are respectivelyconnected to a first precursor supply and a second precursor supply.However, in other embodiments, the manifold may include a single outletwhich may be connected to a single precursor port.

In certain embodiments, it may be preferred to heat manifold 600. FIG.21 shows a heater associated with the manifold. A heater block half 602is shown. The heater block may be made from a conductive material suchas aluminum. This heater block has grooves machined, to allow fitting ofthe manifold and VCR connections. FIG. 22 shows a top view of themanifold heater assembly 600. Here, halves 602 and 604 are shown inintimate contact. Sheet metal reflector plates 606 and 608 are againused to keep the heat inside.

An RTD temperature sensor 136 is shown in FIG. 7A. The sensor measuresthe temperature of the reactor base wall, but because of the closeproximity of its sensitive tip to the O-ring and direct mechanicalcontact between the lid and the reactor base section, the sensor mayallow for indication of wall, O-ring and top lid temperature. Inembodiments when the lid is made of high thermal conductivity material(such as aluminum), the lid temperature may be in thermal equilibriumwith the wall temperature, and evenly distribute the heat from tubularwall heater 126. Such a construction may be preferred in certainembodiments.

FIGS. 8 and 9 show how the reactor base is connected to the cabinet topaccording to one embodiment of the invention. Tubular heater 126 isfixed to a semicircular cutout in the reactor bottom using four bolts128. As shown, the same four bolts 128 are used to fix the reactor tothe cabinet: bolts 128 match holes 420 and the height of the reactorabove the cabinet can be adjusted by altering the position of the nut onbolt 128. A vertical separation between reactor 102 and cabinet top 404provides insulation between reactor bottom and cabinet top and allowsheat to be dissipated and not transferred to the inside of the cabinet,which advantageously can keep the pump and electronics inside cool. Theholding bolts 128 may be made of a low thermal conductivity material(e.g., stainless steel) and have a relatively small cross section, tolimit transfer of heat from the reactor to the cabinet.

RTD temperature sensors 422 and 423 are fixed to the cabinet. Uponremoval of the reactor from the cabinet, for cleaning or other purposes,the RTDs slide from their matching holes 134 and 130. This facilitatesdisassembly of the system.

As shown in FIG. 8, heating of the reactor is controlled via substrateheater 124 and wall-lid tubular heater 126. As noted above, theseheaters may be positioned on the outside of the reaction chamber. Forexample, substrate heater 124 is mounted outside of the reactionchamber, to avoid contamination inside the reaction space and preventthe need for electrical vacuum feedthroughs. In embodiments that includea thin reactor bottom made of a low thermal conductivity material (e.g.,stainless steel), heat transfer is limited from the center of thechamber to the sidewalls and vice versa, permitting individual controlof both sections. The thin reactor bottom portion 138 between substrateheater and wall heater section Is shown more clearly in the crosssection of the reactor, FIG. 11B.

For reactors where the desired deposition temperature does not exceedthe allowable reactor O-ring temperature, differential heating of thereactor using a separate substrate heater and tubular wall heater can beavoided, and one uniform heater can be mounted to the bottom of thereactor. In these embodiments, the bottom of the reactor can be thicker,and made of a higher thermal conductivity material, if so desired.

FIGS. 10 and 11B show locations of the two precursor ports and thepumping line port (i.e., outlet, port) in this embodiment. The substratearea, is located in-between. In addition to the above-describedadvantages, because the precursor and outlet ports are located on thebottom and not on the side of reactor 102, the height of the reactorspace 140 can be very small. Without complicating manufacture orassembly, this improves gas flow and allows low vapor doses. For verythick samples, the top lid can be easily replaced by a lid 142 with avertically ascending cavity 144, as shown in FIG. 12A. If desired, thereaction chamber can also be decreased in volume, by using a lid with asurface protruding into the reaction chamber (FIG. 12B).

FIG. 13 shows a screenshot of the control software during a depositionrun. As can be seen, the substrate temperature (300° C.) is controlledindependently from the wall-lid temperature (130° C.). Separate pressurepulses are observed in mode 1 ALD operation, as described further below.

FIG. 14 shows the thickness results of a run with TMA and waterprecursors after a 900 cycle run on a 4-inch wafer using an ALD systemand method of the present invention. The thickness is measured with anellipsometer and the variation across a four inch wafer is less than 1%.Although the example shown in FIG. 14 is for a 4-inch wafer, it shouldbe understood that the present invention can be used for a wide varietyof samples including wafers of any suitable dimension, or non-wafersubstrates.

Certain embodiments of the invention may use a programmable logiccontroller (PLC), which by definition contains an on board processor forautonomous process control. However, in some embodiments, accuratetiming between valve pulses and accurate, start and end of a processrun, only the valve pulse time itself needs to be controlled beyonddirect PC control capabilities: the pump/purge time between pulses is ofthe order of several seconds and falls well within the realm of direct USB PC control of a logics card with solid state relays, which istypically around 20 milliseconds. The valve pulse time usually has to beanywhere around 1-1.00 milliseconds, and needs to be controlledaccurately. A simple pulse time code provision on a non-autonomouscontrol card can be sufficient in certain embodiments of the inventionand can satisfy this requirement without the need to employ a PLC whichcan be expensive.

FIGS. 24 and 25 illustrate components of a system that includes a singleprecursor port 620 formed in a bottom surface 622 of the reactor chamberaccording to an embodiment of the present invention. As shown, thesingle precursor port is positioned on an opposite side of the substratefrom outlet port 624 (which may be connected to a vacuum). In certainembodiments, a single precursor port may be preferred. For example, incertain embodiments, a single precursor port can increase uniformity ofprecursor flow within the system.

In this illustrative embodiment, first precursor supply 16 and secondprecursor supply 18 are connected to respective inlets 625 a, 625 b of amanifold 626. It is also possible for additional precursor supplies tobe connected to respective inlets of the manifold in other embodimentsof the invention. The manifold includes a single outlet 628 connected toprecursor port 620. As described above in connection with the two portembodiment, pulse valves 206, 208 may provide connection to inert gassupplies. The operation of the pulse valves is similar to that describedabove.

In certain embodiments of the invention, a trap material may be used toadsorb un-reacted precursor that, is being removed from the reactionchamber (e.g., through the outlet pump). In particular, in ALDprocesses, such un-reacted precursor can deposit on system components(such as vacuum gauges, vacuum valves, vacuum lines, and even the vacuumpump) which can impair performance (e.g., concentration measurement bygauge) and may require cleaning.

The trap material may he positioned in the precursor flow path betweenthe reaction chamber and the vacuum gauge. In certain embodiments, itmay be preferred for the trap material to be positioned (at least inpart, and, in some cases, entirely) in the outlet port. FIG. 26 shows atrap 630 positioned in outlet port 624 according to one embodiment ofthe invention. Positioning the trap in the outlet port may heparticularly preferred to facilitate trap replacement.

During operation, the trap typically is maintained at an elevatedtemperature. In some embodiments (e.g., when the trap is positioned, atleast in part, in the outlet port), the trap is heated to a sufficienttemperature by thermal conductance from the reaction chamber (which, forexample, is heated by a tubular heater). Thus, in these embodiments, thetrap does not need to have a separate heater.

In general, any suitable trap may be used, though certain trap designsmay be preferred as described further below. Typical conventional trapexamples include stainless wool, aluminum wool, copper wool, activatedcarbon and activated alumina, amongst others. Characteristics that canbe desirable in trap materials include one or more of the following: (a)surface area sufficiently large not to let excess precursor passtherethrough, but sufficiently small (or free of pores that are toosmall) not to trap all chemicals and/or cause backdiffusion into thechamber (e.g., a surface area between 5 and 100 times the effectivesurface area upstream of the trap which includes (at least) thesubstrate surface area and the surface area inside the chamber); (b)small, flow resistance; (c) allows the same deposition process to occuron the trap as it does on the substrate; (d) passes reaction productstherethrough without trapping, to enable measurement of the reactionproduct (which is related to the original precursor amount, and relatedto the deposited film surface); (e) made of a material with a similarexpansion coefficient as the deposited materials, particularly forceramic coatings; (f) allows coating of many deposition runs withoutfilling up; (g) manufacturable at low cost; and (h) does not create dustor break parts that can break the vacuum pump.

In some embodiments, it may be preferred for the majority of the surfacearea (e.g., greater than 50%, greater than 75%, greater than 95%, etc.)of the trap to be substantially parallel to the flow of gaseous speciestherethrough. In certain cases, substantially all (i.e., greater than99%) of the surface area of the trap is parallel to the flow of gaseousspecies therethrough. This facilitates deposition of the precursor ontrap surfaces, reduces flow resistance and can promote flow of reactionproduct therethrough, In some of these embodiments, the trap includes atleast a portion having a corrugated surface. In some cases, the trap mayinclude both a corrugated surface portion and a flat surface portion.The corrugated surface portion may be a separate component from a flatsurface portion component and the two components may be assembledtogether; or, the corrugated surface portion and flat surface portionmay be different portions of the same component.

In certain embodiments, the trap may be formed of material(s) that arenon-porous.

When the corrugated surface portion and the flat surface portion areseparate components, the trap may be a coil assembly of a flat thin foilrolled together with a corrugated thin foil as shown in FIG. 27. Thesurface area of such a trap can be controlled by tuning the length,diameter and corrugation of the element. The flow resistance of such atrap can be very low because the metal foil surface is very smooth andnot porous, nor does it have any substantial surface area or wiresperpendicular to the flow, in addition, the open area percentage can bevery large because the thickness of the metal foil can much smaller thanthe pore size (corrugation). Typically the thickness of the foil wouldbe around 5-25 micrometer and the pore size 100-1000 micrometer.Typically, in atomic layer deposition processes, films grow on allsurfaces, but since flow passes over the surface of this corrugated trapfoil in much the same way it goes over the substrate, typical depositioncharacteristics will be the same. Because the trap foil has a smoothsurface, volatile phase reaction products generally do not stick to thetrap in much the same way these reaction products do not getincorporated into the film grown on the sample surface during ALD. Thus,the precursor can react on the surface of the trap, until it is depletedbecause the surface area is large, and pass through the volatilereaction product to the gauge for measurement, and then to the vacuumpump to remove from the chamber.

Since the foil can be made of virtually any metal, and the metals can bechosen for their thermal expansion coefficient to match the depositedcoating, delamination and flaking of deposited coating from the trapduring heating and cooling can be limited. For typically depositedceramics, which have low flexibility themselves, expansion engineeredmetals can be used for the foil, such as kovar. Invar and otherexpansion engineered alloys. For typical processes that, deposit Al₂O₃,molybdenum can be effectively used as a foil material, since it isunreactive, strong, and has a thermal expansion coefficient similar tothat of Al₂O₃. The pore sizes of the illustrated trap are typically ofthe order of 100-1000 micrometers, allowing deposition of at least halfthat amount. Typically deposited coatings in one ALD run are of theorder of 10 -100 nm, allowing almost 1000 runs before needing to replaceor etch the trap material. Thin metal foils are low cost, readilyavailable, and can be easily cut, stamped and rolled into the propercoil size. In contrast to ceramic materials and thin metal wires, whichcan form dust and particulates, the coiled foil is a stable, shape whenwelded at the end and will not crack or break.

In some embodiments, the trap can be designed such that a user canvisually observe precursor material deposited on the trap surface,during use, upon removal of the trap from the system. The precursordeposited on the trap was not deposited on the substrate in the ALDprocess and, therefore, is considered precursor “overdose”. The user maydetermine by eye the distance the precursor has deposited on trapsurfaces along the length of the trap. This distance is correlated tothe overdose (e.g., greater distances represent larger overdoses). Trapshaving the majority of their surface area substantially parallel to theflow of gaseous species therethrough (e.g., as shown in FIG. 27) areparticularly preferred in these embodiments. This “overdose” informationmay be used to adjust process parameters to ensure that the overdose isnot too large or too small.

However, it should be understood that other trap materials known in theart may be used in certain embodiments of the invention.

It should be understood that depositions systems of the invention mayhave a variety of other designs not specifically shown, or described,herein. Variations would be known to those of ordinary skill in the art.For example, systems may include any combination of input and outputports (e.g., 5 input ports with one output port, 2 input ports with 2output ports, etc). In addition to separate input ports, also input portmanifolds can be used, where several input port assemblies, includingcylinders and valves, are combined with manifold, the output of which isconnected to the bottom of the reactor base. In addition to using twoinput ports on the reactor, it is also possible to use just one inputport, and use a manifold to expand to 2, 3, 4, 5, etc, precursor lines.

Not excluding other modes of operation, such as for example multilayerand nanolaminate deposition, for illustration purposes, ALD operationcan be grouped into four deposition modes: 1. pulsing precursors whilecontinuously pumping, 2. continuously flowing inert gas while pulsing(adding) precursor and pumping continuously; 3. pulsing precursor with astop valve closed and pumping in-between pulses; 4. pulsing precursorsand purging/pumping with inert gas. In this mode, a stop-valve is avalve that isolates the pump from the reaction chamber and allows theprecursor to remain in the reaction chamber until reacted or removedwhen opening the stop valve. The stop valve is also called a pumpingvalve or vacuum valve.

FIG. 2A shows a deposition cycle with two precursor valve pulses 50 and52. Pulse width is typically 5 milliseconds, and usually shorter thanthe pump time between the pulses. FIG. 2B shows the first mode ofoperation in a pressure-time schematical sketch. While pumpingcontinuously on a chamber, precursor 1 is pulsed, giving peak pressure55, followed by a period of evacuation. The second precursor pulse givesa second pressure rise 57, followed by a second evacuation. Thissequence is repeated until the desired film thickness is achieved. Thevalves, for example, may be solenoid valves such as parker 99 seriesvalves or pneumatic valves such as Swagelok ALD valves.

FIG. 2C shows the second mode of operation in a pressure-timeschematical sketch. While pumping continuously on a chamber whileflowing an inert carrier gas such as nitrogen, base pressure 60 isgenerated in the substrate chamber. When precursor 1 is pulsed, pressure61 is generated, consisting of inert gas pressure+precursor partialpressure. This pulse is followed by a period of inert gas flow and itscorresponding pressure 62. The second precursor pulse gives a secondpressure rise 63, followed by a second inert gas purge 64. This sequenceis repeated until the desired film thickness is achieved.

FIG. 2D shows the third mode of operation in a pressure-time schematicalsketch. After pumping continuously on a chamber during time 66, thestop-valve is closed. After this, precursor 1 is pulsed, giving peakpressure 70. After time-pressure 70, the stop valve is opened and theunreacted precursor portion is removed and the chamber evacuated, givinglow pressure 68. This is followed by closing the stop valve and pulsingthe second precursor, giving time-pressure 69. This is again followed byopening of the stop-valve and evacuating the reaction chamber, givinglow pressure 70. Because of its self-limiting nature, the thickness islargely independent of flow. The consequence is an unequaledconformality over 3 dimensional structures such as trenches and wires.

A wide variety of materials (and combinations of materials) may bedeposited on a wide variety of different substrates using the systemsand methods of the invention. Such coated substrates may be used in anumber of different applications. One application includes scratchresistant color coatings formed on substrates such as metals, plasticsand glass. The coatings may be formed of, for example, TiO2, Zr3N4, Cu,etc, Nanolaminates, consisting of different materials stacked on top ofeach other, with different refractive indices, may enhance this scratchresistance. ALD is particularly attractive for scratch resistant colorcoatings because the ALD technique allows deposition on complex 3Dgeometries and at low temperatures.

Having thus described several aspects of at least one embodiment of thisinvention, it is to be appreciated various alterations, modifications,and improvements will readily occur to those, skilled in the art. Suchalterations, modifications, and improvements are intended to be part ofthis disclosure, and are intended to be within the spirit and scope ofthe invention. Accordingly, the foregoing description and drawings areby way of example only.

What is claimed is:
 1. An atomic layer deposition process comprising:positioning a substrate in a reaction chamber having a top surface, abottom surface and a sidewall between the top and bottom surfaces;introducing a first precursor into the reaction chamber through aprecursor port formed in the bottom surface; removing gaseous speciesthrough an outlet port formed in the bottom surface; introducing asecond precursor in to the reaction chamber through a precursor portformed in the bottom surface; and removing gaseous species through theoutlet port formed in the bottom surface.
 2. The process of claim 1,further comprising introducing an inert gas into the reaction chamber.3. The process of claim 1, wherein introducing the first precursorcomprises pulsing the first precursor and introducing the secondprecursor comprises pulsing the second precursor.
 4. The process ofclaim 1, wherein a layer of the first precursor is deposited on thesubstrate by pulsing the first precursor and a layer of the secondprecursor is deposited on the monolayer of the first precursor bypulsing the second precursor, the first precursor and the secondprecursor reacting to form a layer comprising a compound.
 5. The processof claim 1, further comprising repeating the steps of pulsing the firstprecursor and pulsing the second precursor.
 6. The process of claim 1,wherein the first precursor and the second precursor are introducedthrough the same precursor port.
 7. A trap designed for use in a vapordeposition system to imp gaseous species, wherein a majority of thesurface area of the trap is substantially parallel to flow of gaseousspecies through the trap.
 8. The trap of claim 7, wherein the trapincludes a corrugated surface.
 9. The trap of claim 7, wherein the trapis a coil assembly including a flat foil portion assembled with acorrugated thin foil portion.
 10. The trap of claim 7, wherein the trapis designed such that a precursor deposition distance along a length ofthe trap may be determined by a user by eye and is correlated to aprecursor overdose.
 11. The trap of claim 1, wherein at least 95% of thesurface area of the trap is substantially parallel to flow of gaseousspecies through the trap.
 12. An atomic layer deposition processcomprising: positioning a substrate in a reaction chamber having a topsurface, a bottom surface and a sidewall between the top and bottomsurfaces; introducing a first precursor into the reaction chamberthrough a precursor port formed in the bottom surface, wherein aprecursor layer of the first precursor is deposited on the substrate;removing gaseous species through an outlet port formed in the bottomsurface; introducing a second precursor into the reaction chamberthrough a precursor port formed in the bottom surface, wherein theprecursor layer and the second precursor react to form a material layeron the substrate; removing gaseous species through the outlet portformed in the bottom surface, continuously introducing an inert gas intoSite reaction chamber during the steps of introducing the firstprecursor, removing gaseous species, introducing the second precursorand removing gaseous species; wherein the first precursor, the secondprecursor and the inert gas are introduced through the same precursorport, wherein gaseous species are continuously removed from the reactionchamber during the process.
 13. The process of claim 12, whereinintroducing the first precursor comprises pulsing the first precursorand introducing fee second precursor comprises pulsing the secondprecursor.
 14. The process of claim 12, further comprising introducingthe first precursor into the reaction chamber directly from theprecursor port formed in the bottom surface and introducing the secondprecursor into the reaction chamber directly from the precursor portformed in the bottom surface.
 15. The process of claim 12, wherein amanifold including an outlet is connected to the precursor port andrespective inlets of the manifold are connected to a first precursorsupply and a second precursor supply.